This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. The ability to adjust to changes in the external light environment is especially important to plant survival because, unlike animals, plants depend on sunlight for photosynthesis and they do not have a neuromuscular system which allows them to move to a more optimum light environment. Plants therefore possess the unique light-sensing photoreceptor molecule phytochrome which enables them to perceive the frequent fluctuations of intensity, direction and spectral quality of light in their environment. Phytochrome is found in nearly all photoautrophic organisms from cyanobacteia to higher plants. Our studies seek to provide new insight into the structure, function and evolution of the phytochrome photoreceptor through comparative analysis of the phytochrome-related proteins from flowering plants, cryptogams and bacteria. Through protein sequence analyses, we hope to learn of the origins of both photosensory and regulatory domains of the phytochrome molecule. These include the GAF/bilin lyase, PAS-related and histidine kinase-related domains found in regulatory molecules found in archae, eukaryae to eukaryae kingdoms of life.